The overall objective of this project is to better understand how apoptosis occurs in normal breast cells in order to understand how breast cancer can be prevented. This proposal aims to characterize apoptosis in human MCF-10A breast cells, which are immortalized, non-tumorigenic, non-estrogen-responsive cells. Specific aims are to:1. Determine the mechanism of apoptosis following growth-factor withdrawalin MCF-10A breast epithelial cells, and specifically determine to what extent mitochondria are involved in apoptosis in these cells. 2. Determine how the mechanism of apoptosis followinggrowth-factor-withdrawal is altered in MCF-10A cells that stably express Bcl-2. 3. Determine the pattern of mitochondrial gene expression during apoptosis in MCF-10A and MCF-10A/Bcl-2 cells.